Recently, content is being frequently shared and voice/video calls made using a device have become general communication methods. However, such communication methods have weak security. Nevertheless, encryption methods for communication between devices are developing because demand for protecting personal information of users of the devices is gradually increasing.
FIG. 1A illustrates a general secret key sharing system 10. In the general secret key sharing system 10, a device receives a secret key distributed by a server, and encrypts data by using the secret key received from the server. However, in the general secret key sharing system 10, the server provides the same secret key to devices, and thus security is vulnerable.
FIG. 1B illustrates a general public key sharing system 20. In the general public key sharing system 10, devices exchange a public key and encrypt data by using the exchanged public key. However, in order to safely exchange the public keys between the devices, each device needs to have a certificate, and the certificate needs to be separately exchanged. Also, when the devices that do not have a certificate exchange a public key, the devices are vulnerable to a man-in-the-middle (MITM) attack.
A method of exchanging a key required for communication between devices through a certain application may be used, but it is difficult for a user to determine a suitable communication method according to circumstances.